Fixes issue 1328.

Fixes issue 1328.

Finds the local minimum or maximum of a Bezier curve along the X
axis in the range of an intersection and shifts intersecting
curves up over this range plus slur padding.

Adds default slur padding to all scripts, as this algorithm makes
them almost just touch with the slur whereas the previous one already
had a bit of padding built into it because it was a generous approximation.